We have translated, in a cell-free system several immediate early (IE) herpes simplex virus type 1 (HSV-1) specific polypeptides using mRNA obtained from cycloheximide (CX)-treated HSV-infected cells. Specifically, we have identified the major IE polypeptide of 175,00 dalton synthesized in a messenger-dependent reticulocyte lysate (MDL) cell-free system. Product identification was confirmed by using monoclonal antiserum directed against HSV-1 infected cell products. We have also isolated late HSV-1 mRNA from infected cells and translated the RNA using a cell-free (MDL) system; several HSV-1 specific products have been identified using monoclonal antibody. Specifically, the interrelated 80,000 and 40,000 dalton proteins, as well as 52,000 dalton polypeptide, have been identified by monoclonal antibodies. The latter protein was immunoprecipitated by the antiserum directed against the HSV-1 major glycosylated capsid protein gpD.